1. Field of the Invention
The invention relates to the femur prosthesis part of a knee joint endoprosthesis, supported by sledges on tibia slide surfaces, and the front connecting bridge of its sledges being provided with an upward-tapering conical pin for engagement by static friction in a matching bore of a stem to be anchored in the femur bone.
2. Description of the Prior Art
It is known from German patent specification No. 2 549 819 to shape femur prosthesis parts of knee joint endoprostheses in such way that the stem to be introduced into the femur bone is provided on the outer periphery with, for example, annular ribs which have a saw tooth-like profile in the longitudinal direction. As a result, the stem can be anchored more readily and irreleasably as a unit in the femoral bone and it can be connected to the sledge part, supported on slide surfaces of the tibia plateaus, by means of an upper conical pin which is insertable with static friction into a corresponding bore in the stem, in order thus to enable the tibia part to be exchanged.
Hitherto, the stem was anchored in the femur bone in such a way that it could become loose after a prolonged period and, above all, it was possible for the stem, when inserted or knocked into the medullary cavity of the femur bone, to penetrate either too deeply or not sufficiently deeply into the medullary cavity, so that a perfect fit of the prosthesis was not achievable in this way under some circumstances.